(a) Field of the Invention
The present invention relates to a method and a system for controlling a running mode change for a hybrid vehicle, which includes processing release of an engine clutch for a hybrid vehicle. More particularly, the present invention relates to a method and a system for controlling a running mode change for a hybrid vehicle that prevents a shock from being generated when releasing an engine clutch when changing from one running mode to another running mode.
(b) Description of the Related Art
Hybrid electric vehicles operate through the use of power from an internal combustion engine and power from a battery. In particular, hybrid vehicles are designed to efficiently combine and use power of the internal combustion engine and a motor. For example, as illustrated in FIG. 1, a hybrid vehicle includes an engine 10, a motor 20, an engine clutch 30, a transmission 40, a differential gear unit 50, a battery 60, an integrated starter-generator (ISG) 70, and wheels 80. The engine clutch 30 controls power transmission between the engine 10 and the motor 20, and the integrated starter-generator (ISG) 70 starts the engine 10 or generates electric power by output of the engine 10.
As further shown, the hybrid vehicle includes a hybrid control unit (HCU) 200 which operates the hybrid electric vehicle; an engine control unit (ECU) 110 operates the engine 10; a motor control unit (MCU) 120 operates the motor 20; a transmission control unit (TCU) 140 operates the transmission 40; and a battery control unit (BCU) 160 which operates the battery 60. The battery control unit 160 may also be referred to as a battery management system (BMS). The integrated starter-generator 70 may also be referred to as a starting/generating motor or a hybrid starter-generator.
The hybrid vehicle may be operated in a driving mode, such as an electric vehicle (EV) mode entirely using power of the motor 20, a hybrid electric vehicle (HEV) mode using torque of the engine 10 as main power and torque of the motor 20 as auxiliary power, and a regenerative braking (RB) mode during braking or when the vehicle runs by inertia. In the RB mode, braking and inertia energy are collected through power generation of the motor 20, and the battery 60 is charged with the collected energy.
The hybrid vehicle may change a running mode according to a running state while being driven. When a running mode of a hybrid vehicle is changed from an HEV mode to an EV mode or from an HEV mode to an RB mode, the engine clutch 30 is released, thus power connection between the engine 10 and the motor 20 is cut off. When a running mode of a hybrid vehicle is changed from an HEV mode to an EV mode or from an HEV mode to an RB mode, operation of the engine 10 is stopped.
While the engine clutch 30 is released, the engine clutch 30 operates as illustrated in FIG. 2. For example, a state of the engine clutch 30 may be changed from a lock-up state (FIG. 2 (A)), through a slip state (FIG. 2 (B)), and to an open state (FIG. 2 (C)). In the lock-up state (FIG. 2 (A)) of the engine clutch 30, since the engine 10 generates mechanical friction torque by inertia rotation power, torque transmitted to the motor 20 and a driving shaft does not exist. However, when passing through the slip state (FIG. 2 (B)), friction torque may transiently occur in the engine clutch 30. The transient friction torque is transmitted to the motor 20 and the driving shaft, thereby causing a shock. The shock may negatively affect drivability.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.